D3.137 - The “Street Cat” Paradox: Low Prevalence but High Disease Burden of Mouse Sensitization in Pediatric Asthma

Mouse sensitization contributes significantly to asthma morbidity, with prevalence ranging from 10-45% in inner-city populations globally. However, its clinical relevance in distinct urban ecologies remains poorly characterized. We sought to define the mouse sensitization phenotype in a pediatric asthma cohort from a metropolis with unusually high densities of stray cats, examining how community-based allergen exposure influences disease severity.

 This real-world cross-sectional study stratified pediatric asthma patients by skin prick test reactivity to Mus musculus. We compared clinical severity markers (number of annual exacerbations, 3-month cumulative inhaled corticosteroid (ICS) dose), immunological profiles, and household characteristics (family size, smoking, pet ownership … etc.) between mouse-sensitized 5.8% (n=9) and non-sensitized (n=145) groups.

Mouse sensitization prevalence in our cohort was remarkably low at 5.8%. However, the disease outcomes were substantially worse. Median annual exacerbation rates were significantly elevated compared to non-sensitized peers (2.0 vs. 0.0 attacks/year; p=0.014). Strikingly, not a single mouse-sensitized patient achieved controlled asthma (0% vs. 25.0%; p=0.046), and this group required nearly 3.5-fold higher mean cumulative ICS doses (1666 vs. 472 mcg over 3 months; p=0.07). Demographically, mouse-sensitized children lived in significantly more crowded households (p=0.012). Every mouse-positive patient showed cat allergen co-sensitization (100% vs. 27.3%; p<0.001), however none (0%) of these families owned cats, strongly suggesting that high-load community exposure drives this pan-mammalian sensitization pattern.

The remarkably low prevalence of mouse sensitization in our cohort (5.8%) contrasts sharply with global inner-city data, a disparity we attribute to the natural rodent control provided by the city's dense stray cat population. Paradoxically, when present, mouse sensitization serves as a critical “red flag” for a severe, treatment-resistant phenotype. Affected children face a triple burden: complete lack of disease control, significantly higher ICS requirements, and frequent exacerbations, often compounded by household size. The unique finding of universal cat co-sensitization without domestic ownership confirms an environment-driven “pan-mammalian” sensitization pattern specific to this urban ecology.